Display control circuit for vacuum fluorescent display

ABSTRACT

The invention provides display control circuits for Vacuum Fluorescent Displays (VFDs). The display control circuit controls a plurality of display units of the VFD and comprises an image signal generator generating a plurality of image signals, a clock signal generator generating a clock signal, and a plurality of control signal generators. Each control signal generator receives one of the image signals and the clock signal, generates a control signal for one of the display unit, and determines the duty cycle of the control signal according to the received image signal and the clock signal. The brightness of one display unit varies with the duty cycles of the corresponding control signal. The clock signal generator comprises a plurality of flip-flops coupled in series and a plurality of logic gates.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to display control circuits for Vacuum FluorescentDisplay (VFD).

2. Description of the Related Art

The fast-growing high-tech industry has incorporated display monitors inmore and more electronic devices; making life easier and more convenientfor humans.

Liquid Crystal Displays (LCDs) are very common in high-tech devices,such as cellular phones, televisions, computer display monitors, andother devices. Compared with Cathode Ray Tubes (CRTs), LCDs have smallersizes and are easier to be assembled in electronic devices. However,LCDs comprise backlight modules resulting in relatively diminishedimages when bright light surrounds the outside of the display, such assunlight.

Compared with LCDs, Vacuum Fluorescent Displays (VFDs) provide highbrightness. Meanwhile, since VFDs can provide clear images despite beingsurrounded by sunlight and the cost of VFDs is cheaper than LCDs, VFDsare a suitable display option for some electronic devices.

VFDs are generally utilized in audio devices, microwave ovens or clocksto display numerals, English letters, or simple patterns. The VFDcomprises a screen. The screen can be divided into a plurality ofdisplay units. To control the brightness and image displayed in thedisplay units, each display unit requires a clock signal and an imagesignal.

Because the display units of the conventional VFD each requires aexclusive clock signal to control the brightness, the conventionaldisplay control circuit of the VFD comprises a plurality of clock signalgenerators generating the clock signals for different display units. Theclock signal generators occupy large circuit area and increaseproduction costs. It is desirable to develop a smaller-sized and cheaperdisplay control circuit to be utilized in VFDs.

BRIEF SUMMARY OF THE INVENTION

The invention provides display control circuits for Vacuum FluorescentDisplays (VFDs). The display control circuit controls a plurality ofdisplay units and comprises an image signal generator generating aplurality of image signals for the display units, a clock signalgenerator generating a clock signal, and a plurality of control signalgenerators corresponding to the display units and each generating acontrol signal according to the clock signal and the corresponding imagesignal to control the corresponding display unit. The clock signalgenerator comprises a plurality of flip-flops coupled in series and aplurality of logic gates. The duty cycle of each control signal iscontrolled by the corresponding control signal generator.

In some embodiments of the invention, clock signal generators aredisclosed. The clock signal generator comprises a reference clock signalgenerator providing a reference clock signal, a plurality of flip-flipscoupled in series, and a logic circuit comprising a plurality of ORgates. The first flip-flop is coupled to the reference clock signalgenerator to receive and process the reference clock signal. Based onthe reference clock signal, each flip-flop generates a processed clocksignal and transmits the processed clock signal to the next flip-flop.The OR gates are coupled to the flip-flops to receive the processedclock signals. The logic circuit outputs a clock signal.

The above and other advantages will become more apparent with referenceto the following description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 shows an embodiment of the display control circuit of theinvention; and

FIG. 2 shows an embodiment of the clock signal generator of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is made for the purpose of illustrating thegeneral principles of the invention and should not be taken in alimiting sense. The scope of the invention is best determined byreference to the appended claims.

FIG. 1 shows an embodiment of the display control circuit of theinvention. The display control circuit 1 controls the display units (notshown in the figure) of a VFD, and comprises a data generator 11, animage signal generator 12, a set of control signal generators 13 and aclock generator 14. There are eight control signal generators 131˜138 inthe set of control signal generators 13 in this embodiment. Each controlsignal generator controls a display unit of the VFD.

As shown in FIG. 1, the data generator 11 is coupled to the image signalgenerator 12 to provide image data 111 for the image signal generator12. The image signal generator 12 is coupled to the control signalgenerators 131˜138. After processing the image data 111, the imagesignal generator 12 generates a plurality of image signals 121˜128 forthe control signal generators 131˜138, respectively. As shown in FIG. 1,the image signal 121 is transmitted to the control signal generator 131,the image signal 122 is transmitted to the control signal generator 132,the image signal 123 is transmitted to the control signal generator 133,and so on.

The clock signal generator 14 is coupled to all control signalgenerators 131˜138 and outputs a clock signal 141. The clock signal 141comprises pulses spaced with specific time units.

FIG. 2 shows an embodiment of the clock signal generator of theinvention. The clock signal generator 14 comprises a reference clocksignal generator 21, a reset signal generator 22, a set of flip-flops 23and a logic circuit 24. In this example, the set of flip-flops 23includes eight flip-flops 231˜238 coupled in series. Each flip-flopcomprises a clock signal input terminal, a first output terminal, asecond output terminal, and a reset signal input terminal. The referenceclock signal generator 21 is coupled to the clock signal input terminalof the first flip-flop 231 and provides a reference clock signal 211 forthe first flip-flop 231. The first output terminal of the firstflip-flop 231 is coupled to an OR gate 241 of the logic circuit 24. Thesecond output terminal of the first flip-flop 231 is coupled to theclock signal input terminal of the second flip-flop 232. Afterprocessing the reference clock signal 211, the first flip-flop 231generates a first clock signal 2311 and transmits the first clock signal2311 to the OR gate 241 via the first output terminal and transmits thefirst clock signal 2311 to the clock signal input terminal of the secondflip-flop 232 via the second output terminal. The first output terminalof the second flip flop 232 is coupled to the OR gate 241 of the logiccircuit 24. The second output terminal of the second flip-flop 232 iscoupled to the clock signal input terminal of the third flip-flop 233.After processing the first clock signal 2311, the second flip-flop 232generates a second clock signal 2312 and transmits the second clocksignal 2312 to the OR gate 241 via the first output terminal andtransmits the second clock signal 2312 to the clock signal inputterminal of the third flip-flop 233 via the second output terminal. Thefirst output terminal of the third flip-flop 233 is coupled to the ORgate 241. The second output terminal of the third flip-flop 233 iscoupled to the clock signal input terminal of the fourth flip-flop 234.After processing the second clock signal 2312, the third flip-flop 233generate a third clock signal 2313 and transmits the third clock signal2313 to the OR gate 241 via the first output terminal and transmits thethird clock signal 2313 to the clock input terminal of the fourthflip-flop 234 via the second output terminal. The first output terminalof the fourth flip-flop 234 is coupled to the OR gate 241. The secondoutput terminal of the fourth flip-flop 234 is coupled to the clocksignal input terminal of the fifth flip-flop 235. After processing thethird clock signal 2313, the fourth flip-flop 234 generates a fourthclock signal 2314 and transmits the fourth clock signal 2314 to the ORgate 241 via the first output terminal and transmits the fourth clocksignal 2314 to the clock signal input terminal of the fifth flip-flop235 via the second output terminal. The first output terminal of thefifth flip-flop 235 is coupled to an OR gate 242 of the logic circuit24. The second output terminal of the fifth flip-flop 245 is coupled tothe clock signal input terminal of the sixth flip-flop 236. Afterprocessing the fourth clock signal 2314, the fifth flip-flop 235generates a fifth clock signal 2315 and transmits the fifth clock signal2315 to the OR gate 242 via the first output terminal and transmits thefifth clock signal 2315 to the clock signal input terminal of the sixthflip-flop 236 via the second output terminal. The first output terminalof the sixth flip-flop 236 is coupled to the OR gate 242. The secondoutput terminal of the sixth flip-flop 236 is coupled to the clocksignal input terminal of the seventh flip-flop 237. After processing thefifth clock signal 2315, the sixth flip-flop 236 generates a sixth clocksignal 2316 and transmits the sixth clock signal 2316 to the OR gate 242via the first output terminal and transmits the sixth clock signal 2316to the clock signal input terminal of the seventh flip-flop 237 via thesecond output terminal. The first output terminal of the seventhflip-flop 237 is coupled to the OR gate 242. The second output terminalof the seventh flip-flop 237 is coupled to the clock signal inputterminal of the eighth flip-flop 238. After processing the sixth clocksignal 2316, the seventh flip-flop 237 generates a seventh clock signal2317 and transmits the seventh clock signal 2317 to the OR gate 242 viathe first output terminal and transmits the seventh clock signal 2317 tothe clock signal input terminal of the eighth flip-flop 238 via thesecond output terminal. The first output terminal of the eighthflip-flop 238 is coupled to the OR gate 242. After processing theseventh clock signal 2317, the eighth flip-flop 238 generates an eighthclock signal 2318 and transmits the eighth clock signal 2318 to the ORgate 242. The reset signal generator 22 provides a reset signal 221 forthe flip-flops 231˜238 to reset the flip-flops 231˜238.

In the embodiment shown in FIG. 2, the clock signal generator 14comprises eight flip-flops 231˜238. The flip-flops 231˜238 repeat thesame process on the reference clock signal 211 eight times. The logiccircuit 24 generates a clock signal 141 having one pulse every 256 (2⁸)time units. Referring to FIG. 1, the clock signal 141 is coupled to thecontrol signal generators 131˜138.

Referring to FIG. 1, after receiving the clock signal 141 outputted fromthe clock signal generator 14, the control signal generators 131˜138process the clock signal 141 individually. The control signal generators131˜138 comprise distinct logic modules so that the control signalsgenerated by the control signal generators 131˜138 have distinct dutycycles. The duty cycle of the control signal determines the time spacingof turning on the corresponding display unit.

Instead of the clock signal generators required in the conventionaldisplay control circuit, the display control circuit disclosed by theinvention only requires one clock signal generator. The circuit size andcost of the display control circuit are reduced by the invention.

While the invention has been described by way of example and in terms ofembodiments, it is to be understood that the invention is not limitedthereto. To the contrary, it is intended to cover various modificationsand similar arrangements (as would be apparent to those skilled in theArt). Therefore, the scope of the appended claims should be accorded tothe broadest interpretation so as to encompass all such modificationsand similar arrangements.

1. A display control circuit for controlling a plurality of displayunits of a Vacuum Fluorescent Display and comprising: an image signalgenerator, generating a plurality of image signals; a clock signalgenerator, comprising: a reference clock signal generator, providing areference clock signal; a reset signal generator, providing a resetsignal; a plurality of flip-flops coupled in series; and a plurality oflogic gates, wherein: each of the flip-flops comprises a reset signalinput terminal receiving the reset signal, a clock signal inputterminal, a first output terminal and a second output terminal; a firstone of the flip-flops is coupled to the reference clock signal generatorto receive the reference clock signal via the clock signal inputterminal thereof, and outputs a first clock signal at the first outputterminal and the second output terminal thereof, and the second outputterminal of the first one of the flip-flops outputs the first clocksignal to the clock signal input terminal of a second one of theflip-flops; the rest of the flip-flops are serially coupled to thesecond one of the flip-flops by the same structure coupling the firstone and the second one of the flip-flops; and the first output terminalsof all flip-flops are coupled to the logic gates to generate a clocksignal; and a plurality of control signal generators, coupled to theimage signal generator to receive the image signals, respectively, andall coupled to the clock signal generator to receive the clock signal,wherein each of the control signal generators generate a control signalaccording to the received image signal and clock signal, and the controlsignals generated by the control signal generators to control theplurality of display units are of different duty cycles.
 2. The displaycontrol circuit as claimed in claim 1, wherein each logic gate isimplemented by an OR gate.
 3. The display control circuit as claimed inclaim 1, wherein the control signal generators each comprises a logicmodule determining the duty cycle of the generated control signal. 4.The display control circuit as claimed in claim 3, wherein the dutycycle of the control signal determines the brightness of thecorresponding display unit.
 5. A clock signal generator, comprising: areference clock signal generator, providing a reference clock signal; aplurality of flip-flops coupled in series, wherein a first one of theflip-flops is coupled to the reference clock signal generator to receivethe reference clock signal and, based on the reference clock signal,each flip-flop generates a processed clock signal; and a logic circuit,comprising a plurality of OR gates coupling to the flip-flops to receivethe processed clock signals and generate a clock signal according to theprocessed clock signals, wherein: each of the flip-flops comprises aclock signal input terminal, a first output terminal, a second outputterminal, and a reset signal input terminal; the first one of theflip-flops receives the reference clock signal via the clock inputterminal thereof and outputs a first clock signal at the first andsecond output terminals thereof, and the first output terminal of thefirst one of the flip-flops outputs the first clock signal to the logiccircuit as the processed clock signal corresponding thereto, and thesecond output terminal of the first one of the flip-flops outputs thefirst clock signal to the clock signal input terminal of a second one ofthe flip-flops; and the rest of the flip-flops are serially coupled tothe second one of the flip-flops by the same structure coupling thefirst one and the second one of the flip-flops; and the first outputterminals of all flip-flops are coupled to the logic circuit to generatethe clock signal.
 6. The clock signal generator as claimed in claim 5,wherein the amount of the flip-flips determines the amount of time unitsspacing two pulses of the clock signal.
 7. The clock signal generator asclaimed in claim 5, further comprising a reset signal generatorgenerating a reset signal to be coupled to the reset signal inputterminals of all of the flip-flops.